TODO: proper TeXinfo documentation.
TODO: actually build examples, bechmarks, things

Libraries are by default put in the 'lib' output when that exists, 'out' otherwise.
Crate info files are by default put in the 'env' output when that exists, 'lib' or 'out' otherwise.
Binaries are by default put in the 'bin' when that output exists, 'out' otherwise.
Examples binaries are put in 'example', or 'bin', or 'out' instead.
Benchmark binaries are put in 'benchmarks', or 'bin', or 'out' instead.

Test binaries are put in 'tests', but keep in mind that currently tests are not compiled by default when cross-compiling (this could change in the future if desired, but for now we keep the behaviour of other build systems).  If this output does not exist, it is put in '.guix-tests' in the working directory instead (and not installed).

Crate types:
  * rlib: equivalent to static libraries (.a) for C, + some metadata
  * staticlib: _not_ static library, but rather the compiled crate _and all its dependencies_ as a single static library
  * ...